What Are Glaciers?
QUICK ANSWER
Glaciers are large, persistent bodies of ice that form from compressed snow and flow under their own weight. They exist in mountains worldwide and as vast ice sheets covering Antarctica and Greenland. Glaciers cover about 10% of Earth's land surface and store about 69% of the world's freshwater.
Glaciers are slow-moving rivers of ice that shape landscapes, store freshwater, and influence global sea level. They form anywhere snowfall exceeds melting over many years, allowing ice to accumulate and eventually flow. Glaciers exist on every continent except Australia and range from small mountain glaciers to massive ice sheets covering entire continents. Understanding glaciers reveals important processes in Earth's climate and water cycle.
What is a glacier?
A glacier is a large mass of ice that forms from compressed snow over many years and flows slowly under its own weight. To qualify as a glacier rather than just an ice patch, the mass must be large enough and persistent enough to deform and flow due to gravity. Smaller permanent snow patches that don't flow aren't technically glaciers. The flow can be very slow (sometimes inches per year) or relatively fast (some glaciers move over 100 feet per day). Glaciers can range from small mountain glaciers a few acres in size to continental ice sheets covering millions of square miles.
What are the main types of glaciers?
Glaciers are classified into several main types. Alpine glaciers (or valley glaciers) form in mountains, often in valleys carved by past glaciers. Cirque glaciers occupy small bowl-shaped basins on mountain sides. Piedmont glaciers form when valley glaciers spread out onto flat land. Ice caps are dome-shaped glaciers covering high terrain. Ice sheets are the largest type, vast continental-scale glaciers like those in Antarctica and Greenland. Tidewater glaciers reach the ocean and produce icebergs through calving. Each type has different flow patterns and effects on landscape.
Where are glaciers found?
Glaciers exist on every continent except Australia, though distribution is uneven. The Antarctic ice sheet contains about 90% of all glacier ice. Greenland's ice sheet contains another 8%. The remaining 2% is distributed across mountain glaciers worldwide. Major glacier regions include: the high Himalayas, the Alps, the Andes, the Rocky Mountains and Cascades in North America, the mountains of Alaska, Patagonia, Iceland, Scandinavia, and many high-altitude tropical regions. Even some equatorial mountains in Africa and South America have glaciers due to high altitude.
How big can glaciers get?
Glaciers range enormously in size. The smallest 'glacierets' (technically just persistent ice patches) can be tens of acres. Typical alpine glaciers are a few miles long. Large valley glaciers can extend over 100 miles. The Antarctic ice sheet is the largest single glacier system, covering about 5.4 million square miles with ice up to 2.5 miles thick. The Greenland ice sheet covers 660,000 square miles up to 2 miles thick. Even individual ice streams within these ice sheets can be larger than entire mountain glacier systems elsewhere.
Glaciers are large persistent bodies of ice that form from compressed snow and flow under their own weight. The main types include alpine glaciers, ice caps, and ice sheets. Most glacier ice (about 98%) is in Antarctica and Greenland, with the rest distributed across mountain glaciers worldwide. They store about 69% of Earth's freshwater and shape landscapes through their movement and erosion.
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